The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched.
Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
Meanwhile, the device-to-device (D2D) technology refers to a technology related to terminals, which are located close to each other, that exchange traffic by forming a direct link without the relay of an existing infrastructure to disperse the load of a base station, such as an evolved Node B (eNB), and transmit over a relatively short distance to reduce the power consumption of the terminal and also to have the advantage of reducing the transmission delay (i.e., latency).
An early-stage D2D communication technology has been developed and standardized in non-licensed bandwidths, such as, wireless fidelity (Wi-Fi) Direct and Bluetooth®. However, technology development and standardization for supporting the D2D communication have been in progress in a cellular system that uses the licensed bandwidth. Typically, a 3rd Generation Partnership Project (3GPP), which is a mobile communication standardization organization, has been undertaking a long term evolution (LTE)-based D2D technical standardization process called proximity-based services (ProSe) as one of the new technologies included in the LTE release 12.
The standardization of the LTE-based D2D technology is in progress to develop a terminal discovery process by which each terminal discovers other terminals in the surrounding areas of the terminal itself, and a D2D communication function directly communicates between adjacent terminals. In regard to the terminal discovery process, discussions are underway for a discovery channel structure, a resource allocation/selection method, a transmission time determination method, and a transmission power determination method.
The D2D discovery process identifies the presence of nearby terminals through a separate signal exchange between terminals in a pre-configured discovery channel, and identifies the proximity of the nearby terminals. In an LTE-based D2D discovery process, each terminal transmits a discovery signal defined by the base station for informing of the presence of the terminal itself to a neighborhood terminal in any sub-frame in a channel for terminal discovery, and performs discovery for the adjacent terminal by receiving discovery signals of other terminals during the other discovery channel interval. At this time, the terminal discovery channel can be allocated to an uplink bandwidth or within uplink time interval, and is designed to allow cellular physical uplink control channel (PUCCH) signal transmission in a terminal discovery channel for the normal operation of a cellular network. Further, to maintain orthogonality between the terminal discovery signals based on the OFDM of a cellular network and to ensure a sufficient distance range, a specification of a guard interval (cyclic prefix (CP)) for terminal discovery signals may be determined as either a normal CP or an extended CP regardless of the specifications for the cellular signals.
On the other hand, in order to mitigate adjacent sub-carrier interference (inter-carrier interference (ICI)) generated during simultaneous scheduling of the terminal discovery signal and the cellular PUCCH signal, a method has been agreed to perform power control in the same way with a terminal discovery signal or a conventional cellular physical uplink shared channel (PUSCH). That is, as the transmission power of the discovery signal is proportional to the distance difference with the base station, the transmission power of the discovery signal is lowered as a D2D terminal (DUE) is closer to the base station. Such a decision mitigates the near-far problem generated at the time of the simultaneous reception of a PUCCH signal and a D2D discovery signal in the base station to improve the problem of a reduced reception signal to interference plus noise power ratio (SINR) of the cellular PUCCH signal due to the D2D discovery signal. However, in the case of DUE adjacent to the base station, there is a problem in that the transmission power of the discovery signal is too low for a sufficient discovery radius to be guaranteed.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.